1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a semiconductor device sealed in a synthetic resin composition.
2. Description of the Prior Art
In recent years, electron circuit parts such as a semiconductor device, resistor, capacitor and coil are more favorably sealed or molded in thermosetting resin, thereby reducing a packaging cost. In this case, low pressure molding type epoxy resin composition is generally accepted as a molding material for the above-mentioned object. However, with respect to the sealing of a semiconductor device such as a transistor, IC elements and LSI elements, the sealing by the prior art epoxy resin composition has been found less advantageous than the hermetic sealing process using glass, metal or ceramics, in that said epoxy resin sealing has lower moisture resistance, thereby reducing the reliable performance of a semiconductor device sealed in said epoxy resin composition. The reason for this is that an epoxy resin composition applied by the customary sealing process contains epoxy resin, additives such as a hardening agent and inorganic filler, and impurities included in the components of said epoxy resin composition tend to be ionized in the presence of moisture. The resultant ions corrode a layer of metal, for example, aluminum used as an electrode of a semiconductor device, thus deteriorating the quality of said electrode metal. This phenomenon is a main factor of lowering the reliability of the semiconductor device.
Assiduous efforts have been made to eliminate the above-mentioned drawbacks accompanying the conventional epoxy resin-sealing process. However, considerable difficulties have been experienced in completely removing particularly sodium and chlorine carried into epoxy resin during its manufacture. To date, therefore, no satisfactory results have been achieved.